The present invention relates to a method for measuring the concentration of saccharides having a low molecular weight and a sensor for measuring the same, especially of the saccharides which are difficult to determine by on line or continuous measurement.
Measuring the concentration of saccharides having a low molecular weight such as glucose, fructose, saccharose and syrup has an increasing importance in various fields.
In the field of medical treatment and examination, it is important to measure the concentration of glucose in blood, i.e., blood sugar level and for a serious case of diabetes requiring an insulin administration, the blood sugar level should be measured automatically in order for the proper amount of insulin to be administered.
In the field of fermentation industry, the concentration of a syrup (a mixture of a low molecular weight sugar such as glucose, fructose or saccharose), which is a nutrient source of microorganisms should always be measured. Also in the field of food industry the measurement of glucose, fructose or saccharose is very important to quality control.
For such requirement in various fields, varieties of a sensor for measuring the concentration of saccharides have been provided. Though a method measuring the refractive index was first proposed, it had a disadvantage in selectivity in saccharides to be measured and thus was replaced by a sensor for measuring the concentration of saccharides, especially glucose, employing immobilized enzymes or immobilized microorganisms. The sensor for measuring the concentration of glucose utilizing the immobilized enzyme or immobilized microorganisms is based on the change of concentration of hydrogen peroxide of oxygen produced by oxidation of glucose by glucoseoxygenase which is immobilized on the membrane. Since the sensor can measure a very small amount of glucose and has a high selectivity, it is partly put to practical use.
However, such sensor employing the immobilized enzymes or immobilized microorganisms has a drawback in that a change of an activity of the enzymes or a change of generating power of the sensor due to the clogging of the membrane wherein the enzymes and the like is immobilized occurs with the lapse of time. Therefore, gain and base should be renewed with each sample and every short time and this makes it difficult to measure continuously.
Further, it is required to sterilize the instruments for using in the field such as medical treatment or examination fermentation industry or food industry. However, the sterilization cannot sufficiently be carried out when the material containing enzyme or microorganism is employed.